Electric circuit interrupter



May 25, l948- R. M. BENNETT ELECTRIC CIRCUIT INTERRUPTER Filed March 23,1945 Inventor: Robert M Berwrjett,

b Zai/05j@ y is Attorney Patented May 25, 1948 ELECTRIC CIRCUITINTERRUPTER Robert M. Bennett, ter County,

. Company, a

Birmingham Township, Ches- Pa., asslgnor to General Electric corporationof New York Application March 23, 1945, Serial No. 584,412

(Cl. 20G-148) Claims.

My invention relates to electric circuit interrupters and moreparticularly to electric circuit interrupter employing a blast of iluidsuch as air, to extinguish the arc ldrawn between relatively separablecontacts.

Gas blast circuit breakers which have been extensively used in recentyears generally are of two kinds, the so-called cross blast breaker andthe axial blast breaker. The cross blast breaker is typified by thedisclosure of United States Letters Patent 2,284,842, Prince et al.,assigned to the same assignee as the present application, while thearial blast breaker is typified by Rankin Patent 2,306,186, grantedDecember 22, 1942, and assigned to the same assignee as the presentapplication. The axial blast breaker lends itself very well for highvoltage outdoor application, but the current limit of an axial blastbreaker is relatively low compared to that of a cross gas blast breaker.It would be desirable to provide a gas blast circuit breaker with thehigh 'current carrying ability of the cross gas blast breaker and thehigh voltage capacity of an axial blast breaker.

it is an object of my invention to provide a new and improved :duidblast circuit interrupter.

it is another object of my invention to provide a high voltage gas blastcircuit breaker or the cross gas blast type wherein higher currents maybe interrupted than in high voltage circuit brealyu ers used.bereitcroreu another object of my invention is to prou vide' highspeed, high voltage, high interrupting capacity fluid blast circuitbreaker of improved construction.

Further objects and advantages of my invena polyphase circuit breaker.

relatively movable l arcing contacts, as will become apparent from thefollowing description. 2 is preferably mounted on a pair of suitableinsulators 3 and 'l and one end of the interrupting unit is connected tothe line terminal indicated at 5. The other end of the interrupting unit2 is preferably connected by a conductor 8 with a set of isolatingcontacts comprising the movable contact arm 'l which engages with astationary contact t connected to line terminal il. The isolating ordisconnecting contacts are supported on suitable insulators ill and ii.

As illustrated in thedrawing, the interrupting unit 2 is horizontallyarranged which is particularly advantageous from the standpoint oi pro-The interrupting unit tection from the weather, as will become apparenttion Will become apparent as the following description proceeds and thefeatures of novelty which characterize my invention will be pointed outwith particularity in the claims annexed to and forming a part of thisspecication.

For a. better understanding of my invention reference may be had to theaccompanying drawing in which Fig. 1 is a somewhat schematic elevationalview of an electric circuit interrupter embodying my invention; Fig. 2is an enlarged view partly in section of a portion of Fig. 1; Fig. 3 isan enlarged sectional view of a portion of Fig. 2, and Fig. fi is a viewtaken on line 4 4 of Fig. 3.

Referring now to the drawing, there is illustrated an electric circuitbreaker generally indicated at l in Fig. 1, comprising an arcextinguishing or circuit interrupting unit generally indicated at 2. Itwill be understood that my invention is applicable either to a singlephase o1- where this is material a from the following description. Suchhorizontal construction requires more ground space, and verticalarrangement can be employed. It should be understood, therefore, thatthe horizontal arrangement disclosed is by way of example only.

My invention is particularly concerned with the construction ofinterrupting unit 2 which embodies-the cross blast principle of arcinterruption. Cross blast circuit breakers have an advantage where highspeed operation is desired5 as contrasted with nozzle type interrupterswhich require the Contact to move through a nozzle or? appreciablelength before interruption can place. .ln a cross blast breaker, on theother hand, the fluid blast is effective the instant the contacts part.The problem of increasing the voltage rating of. cross blast circuitinterrupters has been under extensive consideration for some time.Previous attempts to increase the voltage rating of the cross blastinterruptor have generally involved increasing the stroke of thecontacts.` It is now recognized that with contacts of reasonable sizeindefinite increase in contact separation simply produces baddistribution of voltage between the contacts. The voltage drop isconcentrated mainly at the tips of the contacts and the maximum gradientis reduced very little by increasing the contact separation. Also,increasing the contact separation has another undesirable effect. Itincreases the voltage stress in the immediate neighborhood in such a waythat failures occur through joints in the insulating structure and as aconsequence thereof the size of the insulating structure must beincreased so that the design is uneconomical. With my arrangement, avery compact design is permitted with little or no chance of failure ofthe insulatlng structure.

As illustrated in Fig. 2, the interrupting unit 2 of my invention is ofthe multibreak type comprising a. plurality of serially arranged sets ofarcing or interrupting contacts I2 and I3. In Fig. 2 only two sets ofarcing contacts are indicated, but it should be understood that morethan two or only one may be utilized, depending upon the voltage ratingof the circuit interrupter. Each set of interrupting contacts isarranged in an arc confining chamber comprising a laminated structuremade up of members I4, I5, I6, I1, I8, I9 and 20. Only one of the arcconfining structures will be described associated with the contacts I2and I3, since they are all identical and the corresponding parts will bedesignated by the same reference numerals in the drawing. The laminatedstructures defining the arc confining chambers are spaced from eachother by suitable insulating means such as the porcelain insulator 2|.Similarly, insulators 22 and 23 are provided at either end of the arcextinguishing unit to space the laminated, arc confining structures fromthe supporting insulators 3 and 4 respectively. The insulators 2|, 22and 23, all preferably formed of a. weather resistant material, such asporcelain, and the laminated arc confining structures described aboveare assembled into a unitary structure as shown in Fig. 2 by means ofbolts 24 formed of insulating material. The laminations I4 to 20,inclusive, and the insulators 2i, 22 and 23 are provided with alignedopenings through which bolts 24 may extend.

The assembly of insulating members held together by bolts 24 aresupported from insulators 3 and 4 by conducting angle members 25 and 28,respectively. The insulating bolts 24, which may be wood rods, or thelike, extend through conducting angle members 25 and 26.

Insulators 2l and 22 and laminations I4 to 20, inclusive, of eachlaminated arc confining structure are provided with aligned openings soas to define a fluid passageway 21 extending from the end ofinterrupting unit 2 adjacent conducting member 25 to the arcing contactsfarthest removed from insulator 3. Fluid passageway 21 is preferablyconnected by means of a conduit 28 to a source of fluid under pressure(not shown) and suitable means, such as a blast valve (also not shown),controls the flow of fluid to passageway 21.

The relatively movable arcing contacts associated with each laminatedarc confining structure, each comprises a pair of stationary cupshapedmembers 29 arranged with their axes disposed substantially along theaxis of interrupting unit 2. The arclng contacts i2 and i3 are adaptedto move into cup-shaped members 291 but are biased by means of springenclosed within cup-shaped members li into contacting engagement, esshown in Fig. 3. It will be obvious that the contacts i2 and i3 are verylight and movement thereof is quite limited, preferably being less thanan inch. Such a cnstruction enables high speed operation to be obtainedboth by virtue of the light weight and the short distance through whichmovement takes place. Contact i2 of the aro confining structure adjecent insulator 3 is connected by a conductor 3E, which is illustrated asa flexible conductor, to conducting member 25. Contact it, associatedwith the arc confining structure adjacent insulator 3, is connected bymeans of. iexible conductor 32 with the contact of the arc conflningstructure adjacent insulator 4. Also contact I3 of the arc confiningstructure adjacent insulator 4 is connected by means of a. nexibleconductor (not shown) with conducting angle member 26. It should beunderstood that sultable passageways in insulators 2|. 22 and 28 will beprovided for these flexible conductors.

At this stage of the description, it will be understood that a blast ofpressure fluid, released into the conduit 28, flows along the passageway21 and is effective both to separate the so-called retracting arcingcontacts I2 and I3 and' to blast to extinction the arcs drawntherebetween. Before the blast is shut ofi, thereby permitting thespring-biased arcing contacts to reclose, the isolating contact arm 1 iscaused to swing open so that a safe isolating gap is provided wherebycurrent is effectively prevented from flowing through the circuitbreaker from line terminal 5 to line terminal 9.

The laminations I4 to 20, inclusive, of the laminated arc confiningstructures comprise a pair of outer laminations I4 and 20 which areidentical in construction and two sets of laniim nations I5 and I9 andI5 and I8, the members of each set also being identical with each other.The laminations IS and I8 are constructed in the manner clearlydisclosed in Fig. 4, and are provided with an upper circular portion anda lower downwardly extending portion. The opening defining passageway 21and the opening through which contacts I2 and I3 extend areinterconnected by a radially extending passage- Way 33. This cutoutpassageway continues below the contact opening where it diverges into arelatively wide exhaust opening 34. The central lamination I1 isprovided with a similar cutout radial passageway 33 which continuesbelow the contact opening for but a short distance where it terminatesabruptly, thereby providing a barrier or partition portion 35 so thatthe arc drawn between the relatively separable contacts is forcedagainst the transverse edge of barrier portion 35 by the fluid blast.The barrier portion 35 of lamination I1 extends considerably below thelowermost extensions of the other laminations.

Laminations I5 and I9 do not have the passageway or cutaway portion 33interconnecting the opening for the relatively movable contacts and theopening defining passageway 21. The lower portions thereof, however, arecut away as indicated at 36 so as to provide a larger exhaust area forthe fluid blast.

In order to provide for further cooling the exhaust gases flowing oneither side of the baffle or partition portion 35 of lamination il, Ipref" erably provide a plurality of parallel arret'. cooling plates (ilformed of copper or other good heat conducting material.

Preferably the iaminations it to 2E? are ienne-d of a suitable gasevolving, insulating mate such as ber, methyl :nethacrylate and the lil:fn certain cases it might be desirable use a semi-resistance material.

Although laminar construction for insulating intelrupter structurepossesses certain advantages of which, among others, may be cited thebenefit of using high dielectric materials which commonly are availableonly in sheet form, and the facility by which complex intera nal pocketsor passages may be fashioned therein; nevertheless, such laminarconstruction attended by offsetting disadvantages, particu larly thehazard ci' interlaminar voltage breaw down. For example, in theembodiment shown by the drawing and assuming that a iluid blast has justextinguished the arcs. the high voltage stress in the region of theseparated contacts is seeking to re-establish an arc through the path ofleast impedance between the separated contacts.' Such a breakdown path(neglecting the presence of the grooves 38) is most likely to be adetour from contact to contact radially outwards through oneinterlaminar Joint, raxially or longitudinally along a short creepagepath on the surface of an adjacent insulated bolt 24, then radiallyinwards through another interlaminar joint; because breakdown across theshortest direct path across the vseparated contacts is precluded by thecontinued blast of fresh high pressure high dielectric extinguishingfluid rushing through the contact gap. 'I'his interlaminar breakdownhazard threatens even though the laminations are cemented together, forcemented joints invariably are electrically weaker than the insulatingmaterial per se.

In order to reduce or eliminate the above described hazard ofinterlaminar breakdown, the

laminations i4 to 20 and the insulators 2|, 22-

and 23 are provided with a substantially circumferential groove 38, asshown in Figs. 3 and 4. 'Ihis circumferential groove completelysurrounds the relatively movable contacts insofar as laminations i4 and20 are concerned and almost completely surrounds the relatively movablecontacts insofar as the other laminatlons are concerned. Grooves 38 areconnected with the passageway 2l so as to be lled with air or other uidat high pressure during the circuit interrupting operation. Thesegrooved, compressed air seals between each of the joints concentricallysurrounding the region of high volt age stress interpose a high strengthdielectric barrier directly in the way of each of the weaker breakdownpaths. In an electrical seal oi this type, it might be supposed that theincreased dielectric strength of the interlaminar `joint is simply ameasure of the actual linear increase in creepage length provided by thewalls of the groove. This, however, is not the case, for it should berecognized that creepage breakdown strength is also commensurate to thedielectric strength of the medium to which the surface of the materialis exposed. For example, it is known that a. breakdown voltage valuealong a unit length of a given material, say maple wood in free air, isincreased a number of times when the same wood is immersed in insulatingoil. Accordingly, the `breakdown strength oi the grooves additionalcreepage length is increased commensurate to the intensity o1 the blastpressure admitted into the channel formeel by the grooves and which maybe several times the normal creepage breakdown strength of theinsulating materials surface in free air. Obviously, for achievingmaximum effect, a groove 38 is required in each of the two abuttingsurfaces of the laminar joint which coact to form a single hollowchannel or insulating seal that cuts through the plane of the joint. Thegrooves 38 should be designed so that the breakdown value due tocreepage around the walls of the grooved sections approximates that ofthe breakdown value due to puncture radially across the groove gap. Fromthe foregoing explanation, it will be obvious that v the provision ofgrooves alone; i. e., filled only with free air, will increase thedielectric strength only in proportion to the actual linear increase inthe creepage length afforded by the groove walls: but that when thegrooved channels are charged with compressed iluid during theinterrupting process in accordance with my invention, the dielectricstrength of the seal is thereby increased in accordance with theincrease in dielectric strength of the iluid due to the latterscompressed state and which phenomenon is well known in the art. Whileother high dielectric strength fluids. such as oil or insulatingcompound, could be used to fill the channel seals thereby improving thebreakdown strength of a laminar joint `using a seal filled only withfree air; we prefer to use the more practical momentarily chargedpressure gas seal in accordance with the chosen embodiment of the patentdrawing. vIn this embodiment, the highest voltage stress is appliedthrough the laminar joints consequent to the opening of the interruptingcontacts I2 and I3 when, immediately following the circuit interruption,the recovery voltage is endeavoring to break through'the path of leastimpedance from contact to contact as previously stated. Accordingly, itwill be appreciated that the admittance of pressure fluid into thegrooves 38, concurrently with supplying pressure fluid for opening thecontacts, provides an advantageous arrangement whereby the .breakdownstrength of the joints is appropriately increased in immediateanticipation o the increase in applied voltage stress about to occur inthe joints. It is desirable to keep the grooves 38 as narrow as possibleconsistent with the desired dielectric strength of the seal., therebyminimizing the bursting force, introduced by the admittance of fluidpressure to the seal, which tends to separate the laminations one fromanother. Mom ii'ig. e, it will be observed that the insulating channelsformed by the coacting grooves 3u branch out from the longitudinal fluidsupply conduit 2l whereby fresh un-ionized uid is introduced to theseals at 'the beginning of each interruption; also that the entrances tothe seals are remote from the exhaust passages about the cooling plates3l? so that the pressure fluid in the lseals ttl continues uri-ionizedand substantially unaected by the arc products, thereby maintaining thehigh dielectric property of the seal during the continuance of theblast.

it will loe obvious with the arrangement described above theinterrupting unit is especially adapted for outdoor application sincethe downwardly opening exhaust passages for the laminated arc confiningstructures areA protected from the weather. If desired, a suitableshield may be provided for protecting the upper portion of eachlaminated structure.

It will be obvious that with my arrangement the number of interruptingcontacts can 'be in-n creased with a consequent increase in voltage that:may be satisfactorily interrupted. Such a construction is particularlyadvantageous from the standpoint of testing the circuit breaker' sinceit may be tested more nearly at its actual rating by applying the testto a single set of arcing contacts. Also with the cross blastconstruction very high currents may be interrupted and the relativelylight contacts provide for very high speed operation.

In viewv of the detailed description included above, the operation ofthe circuit interrupter embodying my invention Will be obvious to thoseskilled in the art and no further discussion will be included herein. Itshould be understood that suitable means for operating and controllingisolating contact arm 1 will be provided such for example as thearrangement disclosed and claimed in copending Boisseau et al.,application, Serial No. 565,834, filed November 30, 1944, and assignedto the same assignee as the present application.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made without departing from myinvention in its broader aspects and I, therefore, aim ln the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In a fluid blast electric circuit interrupter comprising a pair ofrelatively separable arcing contacts, an arc confining chambercomprising a laminated structure with openings through the laminationsfor said relatively separable contacts, and means including a groove inthe adjacent surfaces of said laminations for defining a channel betweeneach of said laminations, said channel being spaced from said arcingchamber and disposed athwart the path of voltage stress existing whensaid contacts are separated for increasing the surface creepage pathalong the adjacent surfaces of said laminations and from one to theother of said contacts ln a direction substantially parallel to saidadjacent surfaces so as to increase the dielectric strength of saidchamber.'

2. In a fluid blast electric circuit interrupter comprising a pluralityof serially arranged cross blast interrupting sections, means forsupplying a blast of are-extinguishing fluid to said sections, a pair ofrelatively separable arcing contacts associated with each interruptingsection, an arc confining chamber foreach interrupting sectioncomprising a laminated structure with openings through the laminationsfor accommodating said relatively separable contacts, means forsupporting said interrupting sections in spaced relationshipmechanically, means for connecting said contacts in series electrically,and means for increasing the electrical breakdown strength betweenadjacent surfaces of said laminations in a, direction substantiallyparallel thereto, comprising grooves in said adjacent surfaces definingcavities substantially surrounding each chamber and connected to saidfluid supply means, said cavities being disposed in spaced relation fromeach chamber in the planes defined by the adjacent surfaces of saidlaminations.

3, In a fluid blast electric circuit interrupter comprising a pluralityof interrupting sections, means for supplying a blast ofarc-extinguishing fluid to said sections, a pair of relatively separablearcing contacts associated with each in.- terrupting section, an arcconfining chamber for each interrupting section comprising a laminatedstructure with openings through the laminations i o1: accommodating saidrelatively separable con tacts, a groove in the adjacent surfaces ofsaid laminations and in spaced relation from each chamber, means forsupporting said interrupting sections in spaced relationshipmechanica-ily, means for connecting said contacts in serieselectrically, and means including said fluid supply means for injectinga supply of fluid under pressure to said grooves between saidlaminations to improve the dielectric strength of said interruptingsections ln a direction substantially parallel to the adjacent surfacesor said laminations.

4. In a fluid blast electric circuit interrupter comprising a pair ofrelatively separable arcing contacts, an arc confining chambercomprising a laminated structure with openings through the laminationsfor said relatively separable contacts, means defining a fluidpassageway through said laminations through which fluid under pressuremay be supplied for the fluid blast at said contacts, and means forincreasing the dielectric strength of said chamber in a directionsubstantially parallel to the adjacent surfaces of said laminations,comprising grooves in the adjacent surfaces ot said laminationsconnected to said fluid passageway and defining channels between saidlaminations which substantially surround said arc-confining chamber andwhich are spaced from said chamber.

5. In a fluid blast electric circuit interrupter comprising a pair ofrelatively separable arcing contacts, an arc confining chambercomprising a laminated structure with openings through the laminationsfor said relatively separable contacts, means defining a fluidpassageway through said laminations through which fluid under pressuremay be supplied for the fluid blast at said contacts, and a fluid sealin the joint between each of said laminations to increase the Voltagebreakdown strength through each said joint comprising a narrowsubstantially circular groove on each face of each of said laminationssurrounding said relatively movable contacts, said grooves beingconnected t0 said fluid passageway so as to be filled with fluid underpressure when fluid under pressure is supplied to said passageway.

6. In a fluid blast electricl circuit interrupter comprising a pair ofrelatively separable arcing contacts, an arc confining chambercomprising a-lam'inated'structure with openings through the laminationsfor said relatively separable contacts,-means-deflning a fluidpassageway through said laminations through which fluid under pressuremay be supplied for the fluid blast at said contacts, and a fluid sealin the joint between each of said laminations to increase the voltagebreakdown strength through each said joint comprising a narrowsubstantially circular groove on each face of each of said laminationswith the grooves on adjacent faces of adjacent disks being coincident,said grooves being connected to said fluid passageway so as to be filledwith fluid when fluid under pressure is supplied to said passageway.

7. In a fluid blast electric circuit interrupter having a pair ofrelatively separable arcing contacts, a plurality of juxtaposedlaminations havlng surface grooves and openings therein, said openingsdefining an arc-confining' chamber in which said contacts are mounted,means for producing a blast of fluid in said chamber when said contactsare separated to extinguish the arc drawn therebetween, and means forimproving the dielectric strength of said chamber at the juxtaposedsurfaces of said laminations in a direction substantially parallelthereto comprising cavities defined by opposing grooves in adjacentlaminations, said cavities being spaced from said chamber, and meansconnecting said fluid supply means and said cavities for supplying aquantity of fluid under pressure to said cavities during acircuit-interrupting operation.

8. Irfan electrical device, an insulating structure interposed betweenpoints of substantially diierent potential, said structure comprising e.pair of insulating members having surfaces disposed in abuttingrelationship is :roem e, jeins therebetween, end means for increasingthe electrical breakdown ereepsge path thzough seid joint in a'iireetion substantially parallel to the abutting surfaces of saidinsulating members comprising an elsngeed groove :in et least one ofsaid surfaces disposed a'thwsl't the psx-ii of Bruitage stress throughsaid Jsint, said groove being spaced imm the edges si said joint.

i?. In an -feleetiieai device, an insulating structure interposed 'tweenpoints of substantially different potential, seid struesure comprisinge, pair si insulating members having surfaces dispose-fi in abuttingrelationship te om s. join-L therebetween, means for increasing sheelectrical breakdown strength threughsaid joint in e. fiirectnnsubstantially parallel te the abutting sur- :fs-ces oi' said insulatingmembers comprising en elongated muove in ai: least one of said suriaeesdisposed athwsrt the path oi vnltage stress through said Joint betweenthe points nf different potential, said groove being spaced from theedges of said joint, and means for charging said groove with uuid underpressure.

lil. 1n an eleetrlcai device, an insulating structure interposed betweenpoints of substantially different potentiel, said structure comprisings.

` other of seid insulating mem-bess, and means for suppiying saidesi/ity with fluid under me@ suren Zilli.

STATES PATENTE Numbei Name Dass Lilwi ilhitney et al Nov. 20, i9342,0%,729 Beiersdorf Ges. 12, i937 2,253l96 Paul Aug. 19, 194i 2,304,529Beker Dec. 8, 21942 2,31%@ Ludwigs et si Mar. 9, 1943 2,331,441 Then etai Oct. l2, i943 2,498,673 Gsmbitts Aug. EL i946

